1. Field of the Invention
This invention relates to the field of thermoelectric generators and, in particular, to thermoelectric generators using thin-film thermoelectric alloys on selected substrates.
2. Description of the Prior Art
Thermoelectric generators have been known for several years. One of the problems associated with thermoelectric generators is in relation to the relatively low efficiency of thermoelectric energy conversions. In some instances the low efficiency can be ignored if the cost of the fuel is relatively low. This is particularly true where use is made of the thermal gradients in oceans, geothermal wells, and industrial waste streams. However, even with this substantially free energy, for the thermoelectric generator to be competitive it must have an output of electrical power that is less expensive than conventional alternatives. Therefore, to be competitive, it is necessary that the cost of building thermoelectric generators be kept to a minimum.
One of the known types of thermoelectric generators comprises thin thermoelectric semiconductor elements, generally less than one millimeter in thickness, covering only a fraction, generally less than one-third, of the surface area of the heat exchanger. The bismuth telluride-antimony selenide compound is well suited for use in such thermoelectric generators, particularly for the low-temperature range, such as about 0.degree. C. to about 200.degree. C. In this type of thermoelectric generator, semiconductor elements are arranged in arrays with equal numbers of n-type and p-type semiconductor elements that are electrically interconnected in a series/parallel pattern chosen to provide a desirable voltage and current. In a modification of the above thermoelectric generator, only one type (either n-type or p-type) is used in each array, but in the generator module the stacked arrays are alternately n-type and p-type.